Field of the Invention
The invention relates to a guide element for an antenna for a fill level meter, wherein the guide element consists of a dielectric material and is used for forming, guiding and emitting electromagnetic radiation. Furthermore, the invention relates to a method for producing such a guide element.
Description of Related Art
Antennae, for which the guide element being discussed here is to be used, are, for example, used in fill level meters operating according to the radar principle. In addition to the guide element, an antenna also has a supply element. The supply element emits electromagnetic radiation and impinges the guide element with the electromagnetic radiation, which then forms, guides and emits the radiation.
The guide element itself, which can be, for example, a lens, is produced of a dielectric material. The use of a plastic, for example PEEK (polyetheretherketone), is suitable for the production of lenses. The dielectric property of the material used is characterized by its dielectric conductivity, which is also called dielectricity or permittivity.
Normally, the materials used for the guide element have a homogeneous distribution of their dielectric properties, for example in that the material is simply employed homogeneously. Thus, the advantage of easy producibility and reproducibility results in manufacture. The forming of the electromagnetic waves supplied into the guide element, then guided in the guide element and emitted from the guide element into free space then takes place essentially in the emitting section of the guide element, i.e., in the transition area between the dielectric material of the guide element and the free space. This transition area simultaneously represents a step-like change of the permittivity and causes a step-like refraction of the electromagnetic waves. By specifically geometrically designing the emitting section, this effect can be used to form smooth wave fronts (see e.g. EP 2105991 A1 or DE 102008008715 A1).
However, it is necessary in several cases to implement different layers of dielectric properties, for example in order to cause an overall greater refraction than can be caused with only one single boundary layer. This generally takes place by applying different dielectric materials layer by layer, which assumes that a respective material availability is given. Furthermore, arbitrary materials cannot be joined to one another, but rather the mechanical, thermal and chemical properties of the materials have to be taken into account when joining different materials.
Such a production can, accordingly, be complicated and expensive, since it consists of many operation steps and a choice of materials that have to be compatible with one another.
Furthermore, the disadvantage arises in the use of layers that areas of the guide element that are not arbitrarily formed and, in particular, areas located within the guide element can have another permittivity.